/*****************************************************************************
 *
 * This file is part of Mapnik (c++ mapping toolkit)
 *
 * Copyright (C) 2021 Artem Pavlenko
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 *****************************************************************************/

#ifndef MAPNIK_EXTEND_CONVERTER_HPP
#define MAPNIK_EXTEND_CONVERTER_HPP

#include <mapnik/vertex.hpp>

#include <mapnik/warning.hpp>
MAPNIK_DISABLE_WARNING_PUSH
MAPNIK_DISABLE_UNUSED_VARIABLE
#include <mapnik/warning_ignore.hpp>
#include <boost/optional.hpp>
#include <boost/msm/back/state_machine.hpp>
#include <boost/msm/front/state_machine_def.hpp>
#include <boost/msm/front/functor_row.hpp>
MAPNIK_DISABLE_WARNING_POP

// stl
#include <cmath>

namespace mapnik
{

namespace detail
{

namespace msm = boost::msm;
namespace mpl = boost::mpl;
using namespace msm::front;

template <typename T>
T extend(T const & v1, T const & v2, double length)
{
    double dx = v2.x - v1.x;
    double dy = v2.y - v1.y;
    double l12 = std::sqrt(dx * dx + dy * dy);
    double coef = 1.0 + length / l12;
    return vertex2d(v1.x + dx * coef,
                    v1.y + dy * coef, v2.cmd);
}

namespace events
{
    struct vertex_event
    {
        vertex_event(vertex2d const & vertex) : vertex(vertex) { }
        vertex2d const & vertex;
    };

    struct move_to : vertex_event { using vertex_event::vertex_event; };
    struct line_to : vertex_event { using vertex_event::vertex_event; };
    struct close : vertex_event { using vertex_event::vertex_event; };
    struct end : vertex_event { using vertex_event::vertex_event; };
}

namespace actions
{
    struct store
    {
        template <class FSM, class EVT, class SourceState, class TargetState>
        void operator()(EVT const & e, FSM & m, SourceState&, TargetState&)
        {
            m.v2 = m.v1;
            m.v1 = e.vertex;
            m.output = boost::none;
        }
    };

    struct output
    {
        template <class FSM, class EVT, class SourceState, class TargetState>
        void operator()(EVT const & e, FSM & m, SourceState&, TargetState&)
        {
            m.output = e.vertex;
        }
    };

    struct store_and_output
    {
        template <class FSM, class EVT, class SourceState, class TargetState>
        void operator()(EVT const & e, FSM & m, SourceState&, TargetState&)
        {
            m.v2 = m.v1;
            m.v1 = e.vertex;
            m.output = m.v2;
        }
    };

    struct output_begin
    {
        template <class FSM, class EVT, class SourceState, class TargetState>
        void operator()(EVT const & e, FSM & m, SourceState&, TargetState&)
        {
            m.v2 = m.v1;
            m.v1 = e.vertex;
            m.output = extend(m.v1, m.v2, m.extend_length);
        }
    };

    struct output_end
    {
        template <class FSM, class EVT, class SourceState, class TargetState>
        void operator()(EVT const & e, FSM & m, SourceState&, TargetState&)
        {
            m.output = extend(m.v2, m.v1, m.extend_length);
            m.v1 = e.vertex;
        }
    };
}

struct extender_def : public msm::front::state_machine_def<extender_def>
{
    using no_exception_thrown = int;
    using no_message_queue = int;

    struct initial : public msm::front::state<> { };
    struct vertex_one : public msm::front::state<> { };
    struct vertex_two : public msm::front::state<> { };
    struct end : public msm::front::state<> { };

    using initial_state = initial;

    struct transition_table : mpl::vector<
        //  Start         Event                Next      Action                Guard
        //  +------------+-----------------+------------+--------------------+------+
        Row < initial    , events::move_to , vertex_one , actions::store            >,
        Row < initial    , events::line_to , vertex_one , actions::store            >,
        Row < initial    , events::close   , initial                                >,
        Row < initial    , events::end     , end        , actions::output           >,
        Row < vertex_one , events::move_to , vertex_one , actions::store_and_output >,
        Row < vertex_one , events::line_to , vertex_two , actions::output_begin     >,
        Row < vertex_one , events::close   , initial    , actions::store_and_output >,
        Row < vertex_one , events::end     , end        , actions::store_and_output >,
        Row < vertex_two , events::move_to , vertex_one , actions::output_end       >,
        Row < vertex_two , events::line_to , vertex_two , actions::store_and_output >,
        Row < vertex_two , events::close   , initial    , actions::output_end       >,
        Row < vertex_two , events::end     , end        , actions::output_end       >,
        Row < end        , events::end     , end        , actions::output           >
    > {};

    extender_def(double extend_length)
        : extend_length(extend_length)
    {
    }

    boost::optional<vertex2d> output;
    vertex2d v1, v2;
    double extend_length;
};

using extender = msm::back::state_machine<extender_def>;

}

template <typename Geometry>
struct extend_converter
{
    extend_converter(Geometry & geom)
        : extend_converter(geom, 0)
    {}

    extend_converter(Geometry & geom, double extend)
        : geom_(geom), extender_(extend)
    {}

    void set_extend(double extend)
    {
        extender_.extend_length = extend;
    }

    unsigned vertex(double * x, double * y)
    {
        using namespace detail;
        vertex2d v;
        do
        {
            v.cmd = geom_.vertex(&v.x, &v.y);
            switch (v.cmd)
            {
                case SEG_MOVETO:
                    extender_.process_event(events::move_to(v));
                    break;
                case SEG_LINETO:
                    extender_.process_event(events::line_to(v));
                    break;
                case SEG_CLOSE:
                    extender_.process_event(events::close(v));
                    break;
                case SEG_END:
                    extender_.process_event(events::end(v));
                    break;
            }
        } while(!extender_.output);

        vertex2d const & output = *extender_.output;
        *x = output.x;
        *y = output.y;
        return output.cmd;
    }

    void rewind(unsigned)
    {
        geom_.rewind(0);
        extender_.start();
    }

private:
    Geometry & geom_;
    detail::extender extender_;
};

}

#endif // MAPNIK_EXTEND_CONVERTER_HPP
